Abstract:

To enhance the durability of the V-shaped belt by allowing the strength
and the heat-radiating property of the resin blocks to stand together at
high levels in the V-shaped belt, which has a plurality of resin blocks
and endless connecting members connecting the resin blocks. The V-shaped
belt includes a plurality of resin blocks arranged in a direction and an
endless connecting member that is impacted into the resin blocks and that
extends in the arrangement direction of the resin blocks. Depressions are
longitudinally and vertically formed in the upside and downside of the
front surface and the rear surface of each resin block. The depressions
are separated from the connecting member and are also separated from the
lateral surfaces of the resin block.

Claims:

1. A V-shaped belt comprising:a plurality of resin blocks each having
first and second longitudinal surfaces, and first and second lateral
surfaces arranged to engage inner surfaces of a sheave, the plurality of
resin blocks arranged side-by-side in a longitudinal direction of the
plurality of resin blocks; andan endless connecting member extending in
the longitudinal direction of the plurality of resin blocks and impacted
into the plurality of resin blocks to connect the plurality of resin
blocks to each other; whereineach of the plurality of resin blocks
include:a depression provided at a center of each of the first and second
longitudinal surfaces and spaced inwardly from the first and second
lateral surfaces, the depressions are exposed to air; andcarbon fibers
arranged adjacent to or at a surface of the depressions so as to conduct
heat from the plurality of resin blocks directly to the surface of the
depressions.

2. A V-shaped belt comprising:a plurality of resin blocks each having
first and second longitudinal surfaces, and first and second lateral
surfaces arranged to engage inner surfaces of a sheave, the plurality of
resin blocks arranged side-by-side in a longitudinal direction of the
plurality of resin blocks; andan endless connecting member extending in
the longitudinal direction of the plurality of resin blocks and impacted
into the plurality of resin blocks to connect the plurality of resin
blocks to each other; whereineach of the plurality of resin blocks
include:a depression provided at a center of each of the first and second
longitudinal surfaces and spaced inwardly from the first and second
lateral surfaces, the depressions are exposed to air; andthe first and
second lateral surfaces extend upwards to a point that is located below
tops of the plurality of resin blocks and corresponds to a maximum
longitudinal width of the plurality of resin blocks; whereinthe
depressions extend from the tops of the plurality of resin blocks to a
point below the point to which the first and lateral surfaces extend
upwards.

3. The V-shaped belt according to claim 2, further comprising:a bottom
depression provided at the center of each of the first and second
longitudinal surfaces and spaced inward from the first and second lateral
surfaces, the bottom depressions being exposed to air; whereinthe first
and second lateral surfaces extend from a lower point above bottoms of
the plurality of resin blocks; andthe bottom depressions in the first and
second longitudinal surfaces extend from the bottoms of the plurality of
resin blocks to a point above the lower point of the first and lateral
surfaces.

4. A V-shaped belt comprising:a plurality of resin blocks each having
first and second longitudinal surfaces, and first and second lateral
surfaces arranged to engage inner surfaces of a sheave, the plurality of
resin blocks arranged side-by-side in a longitudinal direction of the
plurality of resin blocks; andan endless connecting member extending in
the longitudinal direction of the plurality of resin blocks and impacted
into the plurality of resin blocks to connect the resin blocks to each
other; whereineach of the plurality of resin blocks include:a depression
provided at a center of each of the first and second longitudinal
surfaces and spaced inwardly from the first and second lateral surfaces,
the depressions are exposed to air; andfirst and second grooves extending
inwards from the first and second lateral surfaces, the endless
connecting member arranged within the first and second grooves, and inner
portions of the first and second grooves angling inward so as to meet at
a single point that defines an innermost point of the first and second
grooves.

5. A V-shaped belt comprising:a plurality of resin blocks each having
first and second longitudinal surfaces and first and second lateral
surfaces arranged to engage inner surfaces of a sheave, the plurality of
resin blocks arranged side-by-side in a longitudinal direction of the
plurality of resin blocks; andan endless connecting member extending in
the longitudinal direction of the plurality of resin blocks and impacted
into the plurality of resin blocks to connect the plurality of resin
blocks to each other; whereineach of the plurality of resin blocks
include:a depression provided at a center of each of the first and second
longitudinal surfaces and spaced inwardly from the first and second
lateral surfaces, the depressions are exposed to air; whereina
cross-sectional shape of a top of each of the plurality of resin blocks
along the center of the first and second longitudinal surfaces is curved
such that air can smoothly flow from the depression on the first
longitudinal surface over the top of each of the plurality of resin
blocks to the depression on the second longitudinal surface.

6. A V-shaped belt comprising:a plurality of resin blocks each having
first and second longitudinal surfaces, and first and second lateral
surfaces arranged to engage inner surfaces of a sheave, the plurality of
resin blocks arranged side-by-side and abutting each other in a
longitudinal direction of the plurality of resin blocks; andan endless
connecting member extending in the longitudinal direction of the
plurality of resin blocks and impacted into the plurality of resin blocks
to connect the plurality of resin blocks to each other; whereineach of
the plurality of resin blocks include:a depression provided at a center
of each of the first and second longitudinal surfaces and spaced inwardly
from the first and second lateral surfaces, the depressions are exposed
to air; andcarbon fibers arranged to conduct heat from the plurality of
resin blocks to a surface of the depressions.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a V-shaped belt, a belt-type
transmission, and a saddle-type vehicle.

[0003]2. Description of Related Art

[0004]Conventionally, a V-shaped belt having a plurality of blocks and an
endless connecting member for connecting the blocks has been used for a
belt-type continuously variable transmission fitted to a motor bicycle or
the like. As the blocks used for such a V-shaped belt, blocks made of
metal such as aluminum, blocks obtained by coating a metal molded
material with a resin, or the like have been known.

[0005]The V-shaped belt is used by winding itself around sheaves (pulleys)
rotating at a high speed or the like. As a result, decrease in weight of
the V-shaped belt has been required to facilitate the high-speed
rotation. Therefore, in order to accomplish the decrease in weight of the
V-shaped belt, it has been suggested that blocks made of resin or
substantial resin (hereinafter, referred to as resin blocks) are used as
the blocks (for example, see Japanese Patent JP-A-2002-147553).

[0006]The V-shaped belt disclosed in Japanese Patent JP-A-2002-147553 is
described with reference to FIGS. 22 and 23. As shown in FIG. 22, the
V-shaped belt 100 comprises a number of resin blocks 101 arranged in a
line and an endless connecting member 102. As shown in FIG. 23(b), each
resin block 101 has a falling H shape as seen from the front side and
grooves 105 are formed inward in both sides of each resin block 101. As
shown in FIG. 22, the connecting members 102 are impacted into the
grooves 105 of each resin block 101. As a result, the resin blocks 101
are connected to each other through the connecting members 102. The
connecting members 102 include a rubber 103 and cores 104 buried in the
rubber 103. Although not shown, the V-shaped belt 100 is wound around a
primary sheave and a secondary sheave of a belt-type continuously
variable transmission.

[0007]A large amount of heat is generated in the V-shaped belt 100 due to
friction with the sheaves. In addition, frictional heat is generated
between the resin blocks 101 and the connecting member 102. Internal heat
is generated in accordance with the unevenness of the connecting members
when they are wound around the sheaves and the like. Accordingly, the
heat easily increases the temperature of the V-shaped belt 100.

[0008]However, resin is a material having thermal conductivity lower than
that of metal. As a result, in the V-shaped belt 100 employing the resin
blocks 101, since heat can easily stay in the resin blocks 101, the
temperatures of the resin blocks 101 and the connecting members 102 are
easily increased. Therefore, the V-shaped belt 100 is not enough from the
point of view of a heat-proof characteristic.

[0009]Therefore, there was suggested a V-shaped belt with an improved
heat-radiating property. In Japanese Patent JP-UM-A-61-97647, it is
disclosed that a V-shaped belt having falling H-shaped resin blocks is
provided with depressions recessed downward in both sides of the top
surface of the resin blocks. In the V-shaped belt, since the
heat-radiating area can be enlarged by the depression and the thermally
conductive distance between external air and engaging portions (portions
in which the resin blocks and the connecting members engage with each
other) which is a frictional heat source can be reduced, efficient
radiation of the frictional heat is accomplished.

[0010]However, in the V-shaped belt disclosed in Japanese Patent
JP-UM-A-61-97647, since the depressions recessed downward are formed in
the top surfaces of the resin blocks, the area of both side surfaces of
the resin blocks which contact the sheaves is reduced. As a result, a
sufficient contact area cannot be guaranteed between the V-shaped belt
and the sheaves, and thus it cannot be said to provide sufficient
strength. Specifically, it is difficult to maintain a high rigidity in
the arrangement direction of the resin blocks (longitudinal rigidity). On
the contrary, when the size of the depressions is decreased in order to
maintain sufficient strength, the heat-radiating area is reduced.
Accordingly, a sufficient cooling effect cannot be obtained.

[0011]In Japanese Patent JP-A-61-286638, it is disclosed that a V-shaped
belt is formed by integrally vulcanizing blocks and an endless belt body,
clearances are formed between the neighboring blocks, and cooling air is
introduced into the clearances between the blocks. Specifically, a
V-shaped belt having falling H-shaped blocks and a V-shaped belt having
blocks obtained by coupling upper blocks and lower blocks each other with
pins are disclosed in Japanese Patent JP-A-61-286638. In the V-shaped
belt having the falling H-shaped blocks, the thickness of both lateral
ends of each block is smaller than that of the center thereof, and thus a
clearance is formed between the neighboring blocks at the lateral ends of
the block. On the other hand, in the V-shaped belt having the blocks
consisting of the upper blocks and the lower blocks, a clearance is
formed not between the neighboring lower blocks but between the
neighboring upper blocks.

[0012]In the V-shaped belt having the falling H-shaped blocks disclosed in
Japanese Patent JP-A-61-286638, since the sufficient contact area cannot
be guaranteed between the sheaves and the V-shaped belt as described
above, it is difficult to maintain the sufficient strength. In addition,
since the clearances between the neighboring blocks reach the belt body
in the V-shaped belt, the strength of the engaging portions of the blocks
with the belt body is insufficient although the blocks and the belt body
are integrally vulcanized.

[0013]In the V-shaped belt having the upper blocks and the lower blocks
disclosed in Japanese Patent JP-A-61-286638, the lower blocks contact the
sheaves but no clearance is formed between the neighboring tower blocks.
As a result, it is possible to guarantee the sufficient contact area
between the sheaves and the V-shaped belt but it is difficult to obtain a
sufficient cooling effect. In the V-shaped belt, some degree of cooling
effect may be obtained from the upper blocks. However, since the upper
blocks and the lower blocks are individual members connected to each
other with the pins, the effective cooling of the upper blocks cannot
necessarily guarantee the cooling of the lower blocks.

[0014]As described above, it is difficult to allow the strength and the
heat-radiating property of the resin blocks to stand together in the
conventional V-shaped belt.

SUMMARY OF THE INVENTION

[0015]The present invention is contrived in view of the above-mentioned
problems and it is an object of the present invention to improve the
durability of the V-shaped belt by allowing the strength and the
heat-radiating property of the resin blocks at a high level in the
V-shaped belt having resin blocks and connecting members.

[0016]According to an aspect of the present invention, there is provided a
V-shaped belt comprising: a plurality of resin blocks arranged in a
direction; and an endless connecting member that extends in the
arrangement direction of the resin blocks and that is impacted into the
resin blocks to connect the resin blocks, wherein a depression recessed
in the arrangement direction of the resin blocks and separated from the
connecting member is formed in each resin block.

[0017]In the V-shaped belt, since the depression recessed in the
arrangement direction is formed in each resin block, it is possible to
enlarge the heat-radiating area of the resin blocks and to introduce the
air between the resin blocks, thereby improving the heat-radiating
property. In addition, since the depression is separated from the
connecting member, the engagement strength between the resin blocks and
the connecting member is not weakened depending upon the shapes of the
depression, and thus it is possible to keep the strength of the V-shaped
belt high. Therefore, it is possible to allow the strength and the
heat-radiating property of the resin blocks to stand together at a high
level, thereby improving the durability of the V-shaped belt.

[0018]According to another aspect of the present invention, there is
provided a V-shaped belt comprising a plurality of resin blocks arranged
in a direction, each resin block having grooves inwardly formed at
vertical centers of both lateral surfaces, and an endless connecting
member that extends in the arrangement direction of the resin blocks and
is impacted into the grooves of the resin blocks to connect the resin
blocks, wherein a depression exposed to air is formed at a lateral center
of each resin block.

[0019]The inventors found out that the portion in a so-called falling
H-shaped resin block in which heat can easily stay is the center portion,
and thus the entire resin block can be efficiently cooled by cooling the
center portion. In the V-shaped belt, the depression exposed to the air
is formed at the center of each falling H-shaped resin block. As a
result, since the portions in which the heat can easily stay can be
directly cooled, it is possible to obtain a sufficient heat-radiating
property without enlarging the depression. Therefore, it is possible to
allow the strength and the heat-radiating property of the resin blocks to
stand together at a high level, thereby improving the durability of the
V-shaped belt.

[0020]According to another aspect of the present invention, there is
provided a V-shaped belt comprising a plurality of resin blocks arranged
in a direction, each resin block having grooves inwardly formed at
vertical centers of both lateral surfaces, and an endless connecting
member that extends in the arrangement direction of the resin blocks and
is impacted into the grooves of the resin blocks to connect the resin
blocks, wherein a depression exposed to air and separated from both
lateral surfaces of the resin blocks is formed in each resin block.

[0021]In the V-shaped belt, since the depression exposed to the air is
formed in each resin block, the heat-radiating property is improved. In
addition, since the depression is separated from both lateral surfaces of
each resin block, it is possible to sufficiently secure the contact area
between the resin block and the sheaves. As a result, it is possible to
keep the strength of the resin blocks high, in spite of the formation of
the depression. Therefore, it is possible to allow the strength and the
heat-radiating property of the resin blocks to stand together at a high
level, thereby improving the durability of the V-shaped belt.

[0022]According to another aspect of the present invention, there is
provided a V-shaped belt comprising a plurality of resin blocks that
contains carbon fiber and is arranged in a direction, and an endless
connecting member that extends in the arrangement direction of the resin
blocks and that is impacted into the resin blocks to connect the resin
blocks, wherein a depression exposed to air is formed in each resin
block.

[0023]In one aspect of the present invention, the carbon fiber has a
thermal conduction characteristic more excellent than the resin blocks
and considered that the carbon fiber is added to the resin blocks at the
same time as forming the depressions in the resin blocks. In the V-shaped
belt, the heat in the resin blocks can be effectively delivered to the
surface of the resin blocks, that is, the surfaces of the depressions,
through the carbon fiber, thereby improving the heat-radiating property.
In addition, since the carbon fiber functions as a reinforcing material,
it is possible to keep the strength of the resin blocks high in spite of
the formation of the depressions. Therefore, it is possible to allow the
strength and the heat-radiating property of the resin blocks to stand
together at a high level, thereby improving the durability of the
V-shaped belt.

[0024]According to the present invention described above, it is possible
to allow the strength and the heat-radiating property of the resin blocks
to stand together, thereby enhancing the durability of the V-shaped belt.
Other features and advantages of the invention will be apparent from the
following detailed description, taken in conjunction with the
accompanying drawings which illustrate, by way of example, various
features of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a side view of a motor bicycle according to an embodiment
of the present invention;

[0026]FIG. 2 is a side view of a power unit;

[0027]FIG. 3 is a cross-sectional view of a belt-type continuously
variable transmission;

[0028]FIG. 4 is a side view of a V-shaped belt according to a first
embodiment;

[0029]FIG. 5 is a cross-sectional view taken along a line V-V of FIG. 4;

[0030]FIG. 6 is an explanatory diagram of a resin block according to the
first embodiment, where FIG. 6(a) is a plan view, FIG. 6(b) is a front
view, and FIG. 6(c) is a side view;

[0031]FIG. 7 is a schematic diagram illustrating a flow of air in the
V-shaped belt;

[0032]FIG. 8 is an explanatory diagram of a resin block according to a
second embodiment, where FIG. 8(a) is a plan view, FIG. 8(b) is a front
view, and FIG. 8(c) is a cross-sectional view taken along a line
VIIIc-VIIIc of FIG. 10(b);

[0033]FIG. 9 is a vertical cross-sectional view of the V-shaped belt
according to the second embodiment;

[0034]FIGS. 10(a)-10(c) are explanatory diagrams of a resin block
according to a third embodiment, wherein FIG. 10(a) is a plan view, FIG.
10(b) is a front view and FIG. 10(c) is a cross-sectional view taken
along a line Xc-Xc of FIG. 10(b);

[0035]FIG. 11(a)-11(c) are explanatory diagrams of a resin block according
to a fourth embodiment, wherein FIG. 11(a) is a plan view, FIG. 11(b) is
a front view and FIG. 11(c) is a cross-sectional view taken along a line
XIc-XIc of FIG. 11(b);

[0036]FIG. 12(a)-12(c) are explanatory diagrams of a resin block according
to a fifth embodiment, wherein FIG. 12(a) is a plan view, FIG. 12(b) is a
front view and FIG. 12(c) is a cross-sectional view taken along a line
XIII-XIIc of FIG. 12(b);

[0037]FIG. 13 is a longitudinal sectional view of the V-shaped belt
according to a sixth embodiment;

[0038]FIG. 14 is a longitudinal sectional view of the V-shaped belt
according to a seventh embodiment;

[0039]FIG. 15 is a longitudinal sectional view of the V-shaped belt
according to an eighth embodiment;

[0040]FIG. 16 is a longitudinal sectional view of the V-shaped belt
according to a ninth embodiment;

[0041]FIG. 17 is a longitudinal sectional view of the V-shaped belt
according to a tenth embodiment;

[0042]FIG. 18 is a longitudinal sectional view of the V-shaped belt
according to an eleventh embodiment;

[0043]FIG. 19 is a longitudinal sectional view of the V-shaped belt
according to a twelfth embodiment;

[0044]FIG. 20 is a longitudinal sectional view of the V-shaped belt
according to a thirteenth embodiment.

[0045]FIG. 21 is a longitudinal sectional view of the V-shaped belt
according to another embodiment;

[0046]FIG. 22 is a side cross-sectional view of a conventional V-shaped
belt; and

[0047]FIG. 23 are explanatory diagrams of a conventional resin block,
wherein FIG. 23(a) is a plan view, FIG. 23(b) is a front view and FIG.
23(c) is a side view.

DETAILED DESCRIPTION OF THE INVENTION

[0048]Now, exemplary embodiments of the present invention will be
described with reference to the drawings, wherein like numerals refer to
like parts throughout.

[0049]FIG. 1 shows a motor bicycle 1 which is an example of a saddle-type
vehicle. The motor bicycle 1 has a frame 2. The frame 2 comprises a head
steering pipe 3, a pair of left and right main pipes 4, and a seat rail 5
placed on each main pipe 4. The steering head pipe 3 is positioned at the
front end of the frame 2 and supports a front wheel 7 through a front
fork 6.

[0050]Each main pipe 4 extends backwardly from the steering head pipe 3.
Each main pipe 4 has a front half portion 4a extending backward and
obliquely downward from the steering head pipe 3, a central portion 4c
extending backward and approximately horizontally from the front half
portion 4a, and a rear half portion 4b backward and obliquely upward from
the central portion 4c.

[0051]The seat rail 5 is placed across the front half portion 4a and the
rear half portion 4b of the pipe 4. The seat rail 5 supports a seat 8 on
which a driver rides. The frame 2 is covered with a vehicle cover 9. The
vehicle cover 9 is disposed continuous to the lower end of the seat 8.

[0052]A rear arm bracket 10 is fixed to the central portion 4c of each
main pipe 4. The rear arm bracket 10 is protruded downward from the
central portion 4c of each main pipe 4. The rear arm bracket 10 supports
a rear arm 11 extending backward. The rear arm 11 is pivotable upward and
downward on a support point of the rear arm bracket 10. A rear wheel 12
is supported by the rear end of the rear arm 11.

[0053]The frame 2 supports a power unit 13 for driving the rear wheel 12.
The power unit 13 includes a 4 cycle single-cylinder engine 14 and a
belt-type continuously variable transmission 15 (see FIG. 2). The power
unit 13 is covered with the vehicle cover 9.

[0054]The engine 14 is suspended from and supported by the front half
portion 4a of the main pipes 4. The engine 14 includes a crank case 16
and a cylinder 17 connected to the crank case 16.

[0055]The crank case 16 receives a crank shaft 18 and a gear reducer (not
shown). As shown in FIG. 3, the crank shaft 18 is supported through
bearings 19a and 19b by the crank case 16. The crank shaft 18 is
horizontally disposed along the vehicle-width direction (lateral
direction in FIG. 3) of the motor bicycle 1.

[0056]As shown in FIG. 1, an output end of the gear transmission is
provided with a drive sprocket 20. The drive sprocket 20 is disposed in
the rear of the crank shaft 18. The center of the rear wheel 12 is
provided with a driven sprocket 21. A chain 22 is wound between the drive
sprocket 20 and the driven sprocket 21.

[0057]The cylinder 17 of the engine 14 is protruded upward from the crank
case 16 along the front half portion 4a of the main pipes 4. As shown in
FIG. 2, the cylinder 17 receives a piston 23. As shown in FIG. 3, the
crank shaft 18 is provided with crank webs 25a and 25b. A crank pin 24a
is provided between the crank webs 25a and 25b. The piston 23 is
connected to the crank pin 24a through a connecting rod 24.

[0058]As shown in FIGS. 2 and 3, The belt-type continuously variable
transmission (hereinafter, referred to as "CVT") 15 is disposed at the
right side of the crank case 16. The right side surface of the crank case
16 is covered with a transmission case 28 and the CVT 15 is received in
the transmission case 28.

[0059]The CVT 15 comprises a primary sheave 29, a secondary sheave 30, and
a V-shaped belt 31 wound on the primary sheave 29 and the secondary
sheave 30. The primary sheave 29 is positioned at the front side in the
transmission case 28 and is supported by an input shaft 32. As shown in
FIG. 3, the input shaft 32 is integrally formed with the crank shaft 18.
A journal portion 18a positioned at the right end of the crank shaft 18
extends to right toward the transmission case 28 (not shown in FIG. 3).
The extending portion also serves as the input shaft 32.

[0060]The primary sheave 29 includes a fixed plate 34a and a sliding plate
34b opposed to the fixed plate 34a. The fixed plate 34a is fixed to the
end of the input shaft 32. Accordingly, the fixed plate 34a rotates
integrally with the input shaft 32. On the other hand, the sliding plate
34b is slidable in the axis direction of the input shaft 32. The sliding
plate 34b has a cylinder-shaped boss portion 35. The boss portion 35 is
supported through a collar 36 by the input shaft 32. As a result, the
sliding plate 34b is slidable in the direction in which the sliding plate
34b moves closer to or apart from the fixed plate 34a and is rotatable
about the input shaft 32.

[0061]The primary sheave 29 has a pair of sandwiching surfaces 37a and 37b
between which the V-shaped belt 31 is sandwiched. Specifically, the
sandwiching surface 37a is formed at the left side of the fixed plate 34a
and the sandwiching surface 37b is formed at the right side of the
sliding plate 34b. The sandwiching surfaces 37a and 37b are formed in a
cone shape and are opposed to each other. The sandwiching surfaces 37a
and 37b define a belt groove 38 having a V-shaped section between the
fixed plate 34a and the sliding plate 34b. The width L1 of the belt
groove 38 can be adjusted by means of sliding of the sliding plate 34b.

[0062]A cam plate 39 is fixed to the left outer circumferential portion of
the input shaft 32. Therefore, the cam plate 39 rotates along with the
input shaft 32. The cam plate 39 is opposed to the sliding plate 34b in
the lateral direction. The sliding plate 34b is mounted to the cam plate
39 and is slidable in the axis direction of the input shaft 32. As a
result, the cam plate 39 and the sliding plate 34b are movable in the
direction in which they get closer to or apart from each other while
rotating together.

[0063]A cam surface 40 opposed to the cam plate 39 is formed at the left
side of the sliding plate 34b. A plurality of weight rollers 41 is
provided between the sliding plate 34b and the cam plate 39 (only one
weight roller 41 is shown in FIG. 3). When the crank shaft 18 rotates, a
centrifugal force is generated in the weight roller 41. The weight roller
41 moves along the cam surface 40 in response to the centrifugal force.
By means of the movement, a force to the right side is applied to the
sliding plate 34b from the weight roller 41, and thus the sliding plate
34b slides in the axis direction of the input shaft 32. As a result, the
width L1 of the belt groove 38 varies.

[0064]The secondary sheave 30 is disposed at the rear side in the
transmission case 28. The secondary sheave 30 is supported by an output
shaft 42. The output shaft 42 is disposed parallel to the input shaft 32
and is connected to an input end of the gear reducer through an automatic
centrifugal clutch (not shown).

[0065]The secondary sheave 30 has a fixed plate 45a and a sliding plate
45b. The rotation center of the fixed plate 45a is provided with a
cylinder-shaped collar 46. The collar 46 engages with the outer
circumferential surface of the output shaft 42. By means of the
engagement, the fixed plate 45a and the output shaft 42 rotate together.

[0066]The rotation center of the sliding plate 45b is provided with a
sleeve 47. The sleeve 47 is fitted onto the outer circumferential surface
of the collar 46 to be slidable in the axis direction thereof. A
plurality of engaging grooves 48 is formed in the sleeve 47. The engaging
grooves 48 extend in the axis direction of the sleeve 47 and are arranged
in the circumferential direction of the sleeve 47 with a separation.

[0067]The collar 46 has a plurality of engaging pins 49. The engaging pins
49 are protruded in the outward radial direction of the collar 46 and are
slidably impacted into the engaging grooves 48 of the sleeve 47. As a
result, the fixed plate 45a and the sliding plate 45b rotate together and
are movable in the direction in which they get closer to or apart from
each other.

[0068]The secondary sheave 30 has a pair of sandwiching surfaces 51a and
51b between where the V-shaped belt 31 is sandwiched. Specifically, the
sandwiching surface 51a is formed at the right side of the fixed plate
45a and the sandwiching surface 51b is formed at the left side of the
sliding plate 45b. The sandwiching surfaces 51a and 51b are formed in a
cone shape and are opposed to each other. The sandwiching surfaces 51a
and 51b define a belt groove 52 having a V-shaped section between the
fixed plate 45a and the sliding plate 45b. The width L2 of the belt
groove 52 can be adjusted by means of sliding of the sliding plate 45b.

[0069]A spring bearing 53 is fixed to the right end of the collar 46. The
spring bearing 53 is laterally opposed to the sliding plate 45b. A
compression coil spring 54 is disposed between the spring bearing 53 and
the sliding plate 45b. The spring 54 biases the sliding plate 45b toward
the fixed plate 45a.

[0070]As shown in FIG. 3, the V-shaped belt 31 is wound around the primary
sheave 29 and the secondary sheave 30. Specifically, the V-shaped belt 31
is impacted into the belt groove 38 of the primary sheave 29 and the belt
groove 52 of the secondary sheave 30. The detailed construction of the
V-shaped belt 31 will be described in greater detail herein below.

[0071]In a state where the number of rotation of the crank shaft 18 is
small (for example, in a state where the engine 14 is under idling or the
like), the centrifugal force acting on the weight roller 41 is small.
Accordingly, the weight roller 41 is positioned at the inner radial side
of the primary sheave 29. In this state, the sliding plate 34b is most
apart from the fixed plate 34a, and the width L1 of the belt groove 38 is
the maximum. As a result, the winding diameter of the V-shaped belt 31 in
the primary sheave 29 is the minimum.

[0072]On the contrary, in the secondary sheave 30, the sliding plate 45b
is biased toward the fixed plate 45a by the spring 54, and thus the belt
width L2 is the minimum. As a result, the V-shaped belt 31 impacted into
the belt groove 52 is extruded toward the outer circumferential portion
of the secondary sheave 30. Consequently, the winding diameter of the
V-shaped belt 31 in the secondary sheave 30 is the maximum.

[0073]In this way, in the state where the number of rotation of the crank
shaft 18 is small, the winding diameter in the primary sheave 29 is the
minimum and the winding diameter in the secondary sheave 30 is the
maximum. As a result, the transmission ratio of the CVT 15 is the
maximum.

[0074]On the other hand, when the number of rotation of the crank shaft 18
is increased, the centrifugal force acting on the weight roller 41 is
increased, and thus the weight roller 41 moves in the outward radial
direction of the sliding plate 34b. As a result, the sliding plate 34b is
pressed to right side by the weight roller 41 and slides toward the fixed
plate 34a. Consequently, the width L1 of the belt groove 38 becomes
smaller slowly. Then, the V-shaped belt 31 sandwiched between the
sandwiching surfaces 37a and 37b is extruded in the outward radial
direction of the primary sheave 29, and thus the winding diameter of the
V-shaped belt 31 in the primary sheave 29 is increased.

[0075]On the contrary, in the secondary sheave 30, the V-shaped belt 31 is
pulled in the inward radial direction of the secondary sheave 30 to be
tight, with increase in winding diameter in the primary sheave 29.
Accordingly, the force acting to the right side is given to the sliding
plate 45b from the V-shaped belt 31, and thus the sliding plate 45b
slides against the biasing force of the spring 54 in the direction in
which the sliding plate 45b gets apart from the fixed plate 45a. As a
result, the width L2 of the belt groove 38 becomes greater slowly.
Consequently, the winding diameter of the V-shaped belt 31 in the
secondary sheave 30 is decreased.

[0076]In this way, when the number of rotation of the crank shaft 18 is
increased, the winding diameter in the primary sheave 29 is increased,
and the winding diameter in the secondary sheave 30 is decreased.
Accordingly, in the CVT 15 described hitherto, the transmission ratio
varies automatically and continuously with the increase in the number of
rotation of the crank shaft 18. In addition, the transmission ratio of
the CVT 15 is the minimum when the winding diameter in the primary sheave
29 is the maximum.

[0077]Next, the detailed construction of the V-shaped belt 31. As shown in
FIGS. 4 and 5, the V-shaped belt 31 comprises a plurality of resin blocks
56a arranged in a direction and a pair of connecting members 57 for
connecting the resin blocks 56a. In the following description, the
longitudinal direction, the lateral direction, and the vertical direction
of the resin blocks 56a are defined as follows for the purpose of
convenient explanation. That is, the longitudinal direction denotes the
arrangement direction of the resin blocks 56a. The surfaces of the resin
blocks 56a contacting the sheaves 29 and 30 are denoted by lateral
surfaces. The portion positioned at the outside in the diameter direction
of the sheaves 29 and 30 when the V-shaped belt 31 is wounded around the
sheaves 29 and 30 is referred to as an upper portion, and the portion
positioned at the inside in the diameter direction is referred to as a
lower portion. However, the respective directions described above are, in
one aspect, defined for the purpose of convenient explanation and do not
necessarily refer to the directions when the V-shaped belt is in use.

[0078]As shown in FIGS. 6(a) to 6(c), each resin block 56a is made of a
thin plate having a small longitudinal width and has both lateral
surfaces 70, an upper surface 71, and a lower surface 72. As shown in
FIG. 6(b), the lateral length of the resin block 56a is decreased from
the upper surface 71 to the lower surface 72, and the resin block 56a is
formed to correspond to the V shape of the belt grooves 38 and 52 of the
sheaves 29 and 30. Grooves 59 are recessed inward in the vertical centers
of both lateral surfaces 70 of the resin block 56a. The grooves 59 are
used to impact the connecting members 57 thereto. In the state where the
connecting members 57 are impacted into the resin block 56a, the groove
59 is not exposed to the air.

[0079]On the other hand, depressions 81 and 82 exposed to the air are
formed in the upper surface 71 and the lower surface 72 of the resin
block 56a. The depressions 81 and 82 are formed from both laterals to the
center of the resin block 56a and recessed in the longitudinal direction
(see FIG. 6(a)). The depressions 81 and 82 are formed in the front
surface and the rear surface of the resin block 56a, respectively. The
longitudinal widths of the upper portion and the lower portion of the
resin block 56a are gradually decreased from both laterals to the center.
However, the depressions 81 and 82 are formed at the center rather than
at both laterals and are not formed at both laterals. Therefore, only
both laterals of the resin block 56a, that is, the portions contacting
the sheaves 29 and 30, have a width greater than other portions by a
width which the depressions are not formed.

[0080]In addition, as shown in FIG. 6(b), the depressions 81 and 82 are
vertically recessed from both laterals of the resin block 56a to the
center. That is, the depressions 81 and 82 are recessed longitudinally
and vertically. The depressions 81 and 82 are inwardly recessed in the
lateral section of the resin block 56a (the section perpendicular to the
arrangement direction of the resin block 56a). In one embodiment, the
degree of recession is increased from both laterals of the resin block
56a to the center and the depressions 81 and 82 are most greatly recessed
at the lateral center.

[0081]As shown in FIG. 6(c), the upper end and the lower end of the resin
block 56a in which the depressions 81 and 82 are formed is tapered toward
both ends. In one embodiment, in the longitudinal section including the
depressions 81 and 82 (the section vertically parallel to the arrangement
direction of the resin blocks 56a), the outline of the ends of the resin
block 56a is curved. The shape of the outline is not particularly limited
and is formed preferably in a quadratic curve such as parabola. The
protruded end of the resin block 56a has a curved surface.

[0082]The resin blocks 56a have a base material made of resin and a
reinforcing material. In one embodiment, carbon fiber is contained as the
reinforcing material in the resin blocks 56a. The carbon fiber has
thermal conductivity that is generally better than the resin material of
the base material. The carbon fiber contained in the resin blocks 56a
performs a function of enhancing the thermal conductivity of the resin
blocks 56a, as well as a function as the reinforcing material. The heat
radiating property of the resin blocks 56a can be improved with an
increase in content of the carbon fiber. The content of the carbon fiber
can be properly set in consideration of a desired strength or
productivity of the resin blocks 56a.

[0083]In one aspect, when a sufficient strength can be realized, the
reinforcing material may be omitted. In some cases, materials other than
the reinforcing material may be contained in the base material. Various
resin materials such as thermoplastic resin, thermosetting resin, and the
like can be used as the base material. The kind of the reinforcing
material is not limited and may properly employ glass fiber, aramid
fiber, or the like, in addition to the carbon fiber. For example, a wear
preventing agent or frictional-coefficient adjusting agent may be
contained in the material other than the reinforcing material.

[0084]In one embodiment, the connecting member 57 is formed endless. As
shown in FIG. 4, the connecting member 57 extends the arrangement
direction of the resin blocks 56a and is impacted into the grooves 59 of
the resin blocks 56a. In this way, by impacting the connecting member 57
into the grooves 59 of the resin blocks 56a, a plurality of resin blocks
56a are connected to each other through the connecting member 57. In one
embodiment, the connecting member 57 can be formed of rubber. The kind of
the rubber constituting the connecting member 57 is not particularly
limited and, for example, super heat-proof rubber may be most preferably
used. As shown in FIG. 5, a plurality of cores 60 for reinforcement can
be buried in the rubber.

[0085]The resin blocks 56a and the connecting member 57 are not integrally
vulcanized. However, the resin blocks 56a and the connecting member 57
may be integrally vulcanized.

[0086]As described hitherto, in the V-shaped belt 31 according to one
embodiment, the depressions 81 and 82 exposed to the air are formed in
the upper side and the lower side of the resin blocks 56a, respectively.
As a result, the heat-radiating area of the resin blocks 56a is enlarged.
That is, the area of the resin blocks 56a contacting the air is enlarged.
Therefore, the heat-radiating property of the resin blocks 56a is
improved.

[0087]As schematically shown in FIG. 7, since the depressions 81 and 82
(the depression 82 is not shown in FIG. 7) are formed in the front
surface and the rear surface of each resin block 56a, clearances 83 are
formed between the neighboring resin blocks 56a. As a result, the air
flows in the clearances 83 with the traveling of the V-shaped belt 31
(see the solid arrows in FIG. 7). Specifically, the clearances 83 are
formed in the traveling direction of the V-shaped belt 31 (the traveling
direction is parallel to the arrangement direction of the resin blocks
56a). The clearances 83 are formed at the front side of the respective
resin blocks 56a in the traveling direction. Therefore, since the
clearances 83 are formed in the portions in which the air can easily
flow, the air actively flows over the surfaces of the resin blocks 56a
with the traveling of the V-shaped belt 31, thereby further improving the
heat-radiating property of the resin blocks 56a.

[0088]When the number of rotation of the sheaves 29 and 30 is increased,
the amount of heat emitted from the V-shaped belt 31 is increased.
However, according to one embodiment, the traveling speed of the V-shaped
belt 31 is increased with increase in the number of rotation of the
sheaves 29 and 30, and thus the flow rate of the air passing through the
clearances 83 is increased. As a result, the increase in the number of
rotation of the sheaves 29 and 30 improves the heat-radiating property of
the resin blocks 56a. Therefore, according to one embodiment, it is
possible to prevent an increase in temperature of the V-shaped belt 31
even in the case of high-speed driving.

[0089]In the V-shaped belt 31 according to one embodiment, the upper end
and the lower end in the longitudinal section of the each resin block 56a
including the depressions 81 and 82 are tapered. As a result, the
clearance 83 is formed in a shape of which the end is widened toward the
opening end, thereby easily introducing air. Therefore, it is possible to
further improve the heat-radiating property of the V-shaped belt 31.

[0090]In the V-shaped belt 31 according to one embodiment, the outline of
the end in the longitudinal section of each resin block 56a is in a
curved line. As a result, since the air can smoothly flow in the
clearances 83 along the curved lines of the resin blocks 56a. That is,
the protruded end of each resin block 56a has a curved surface and the
protruded is rounded, the air can smoothly flow in the clearance 83.
Therefore, it is possible to more efficiently accomplish the
heat-radiation.

[0091]In one aspect, the depressions 81 and 82 are formed at the lateral
center of each resin block 56a. As a result, the center at which heat can
most easily stay in each resin block 56a can be efficiently cooled.

[0092]In the V-shaped belt 31 according to one embodiment, since the resin
blocks 56a have an excellent heat-radiating property; heat difficulty
stays in the resin blocks 56a. As a result, it is possible to prevent the
excessive increase in temperature of the resin blocks 56a and the
connecting member 57. In addition, since the heat-proof characteristic of
the V-shaped belt 31 is improved, it is possible enhance the reliability
of the V-shaped belt 31.

[0093]In the V-shaped belt 31 according to one embodiment, the depressions
81 and 82 are formed at the center side rather than both laterals of each
resin block 56a. In other words, the depressions 81 and 82 are formed in
the portions other than both laterals and are separated from both lateral
surfaces 70 of each resin block 56a. As a result, although the
depressions 81 and 82 are provided, the area of the contact portions of
the resin blocks 56a with the sheaves 29 and 30 can be sufficiently
guaranteed, and thus the strength of the contact portions can be kept
well.

[0094]In addition, in the V-shaped belt 31 according to one embodiment,
the depressions 81 and 82 do not reach the connecting member 57 but are
separated from the connecting member 57. In other words, the depressions
81 and 82 are formed in the portions into which the connecting member 57
is not impacted. As a result, although the depressions 81 and 82 are
provided, the strength of the engaging portions of the resin blocks 56a
with the connecting member 57 cannot be decreased greatly. Therefore, it
is possible to maintain the high strength of the resin blocks 56a.

[0095]In one aspect, the carbon fiber is contained in the resin blocks 56a
of the V-shaped belt 31. As a result, the heat in the resin blocks 56a
can be delivered to the surfaces of the resin blocks 56a (specifically,
the surfaces of the depressions 81 and 82 with a high cooling effect)
through the carbon fiber, thereby further improving the heat-radiating
property. In addition, since the carbon fiber functions as the
reinforcing material, it is possible to maintain the high strength of the
resin blocks 56a in spite of the depressions 81 and 82.

[0096]In the V-shaped belt 31 according to one embodiment, it is possible
for the strength and the heat-radiating property of the resin blocks 56a
to stand together at a high level. Therefore, it is possible to improve
the durability of the V-shaped belt 31.

[0097]According to one embodiment, since the deterioration of the V-shaped
belt 31 due to the heat emission can be suppressed, it is possible to
improve the reliability of the CVT 15. In addition, since the V-shaped
belt 31 is not deteriorated easily even at the time of high-speed
driving, it is possible to enlarge the allowable operation range of the
CVT 15. The improvement of the reliability of the CVT 15 also improves
the reliability of the motor bicycle 1. The enlargement of the allowable
operation range of the CVT 15 can improve the degree of freedom in
designing the engine 14.

[0098]Next, a V-shaped belt 31 according to other embodiments of the
present invention will be described. In the embodiments described below,
the V-shaped belt 31 comprises a plurality of resin blocks and a
connecting member. Since the connecting member is similar to the first
embodiment, description thereof will be omitted. Hereinafter, the resin
blocks are described mainly. The same elements as the first embodiment
are denoted by the same reference numerals and description thereof will
be omitted.

[0099]FIGS. 8(a) to 8(c) show a resin block 56b of the V-shaped belt 31
according to a second embodiment. Similarly to the resin block 56a
according to the first embodiment, depression 81 is formed in the upper
front and rear surfaces of the resin block 56b and depression 82 is
formed in the lower front and rear surfaces of the resin block 56b
according to the second embodiment. However, the depressions 81 and 82 of
the resin block 56b are recessed in a step shape, and thus a step
difference is formed in the boundaries of the depressions 81 and 82.

[0100]As shown in FIG. 8(a), the longitudinal width of the resin block 56b
is decreased from both lateral ends to the center step-like. The
longitudinal width of the depression 81 is constant. As shown in FIG.
8(b), the upper depression 81 is vertically recessed toward the center of
the resin block 56b. In one aspect, the vertical length of the depression
81 is constant almost all over the lateral direction and the bottom side
of the depression 81 is parallel to the upper surface 71 of the resin
block 56b. The lower depression 82 is also vertically recessed to the
center of the resin block 56b. The vertical length of the depression 82
is constant almost all over the lateral direction. As shown in FIG. 8(c),
the upper portion and the lower portion of the resin block 56b has a
width smaller than that of the vertical center.

[0101]Therefore, as shown in FIG. 9, in the V-shaped belt 31 according to
the second embodiment, the heat-radiating area of the resin blocks 56b is
enlarged and clearances 83 are formed between the neighboring resin
blocks 56b. As a result, the heat-radiating property of the resin blocks
56b can be improved, and the heat can be prevented from staying in the
resin blocks 56b. Therefore, it is possible to suppress the deterioration
of the V-shaped belt 31 due to the generation of heat. FIG. 9 is a
longitudinal sectional view of the V-shaped belt 31 including the
depressions 81 and 82, where the hatching marks indicating a section are
omitted. The same is true of all the following figures.

[0102]FIGS. 10(a) to 10(c) show a resin block 56c of a V-shaped belt 31
according to a third embodiment. Two depressions 81 laterally arranged
are formed in each of the upper front and rear surfaces of the resin
block 56c. A depression 82 is formed in each of the lower front and rear
surfaces. Similar to the second embodiment, the depressions 81 and 82 are
recessed in a step shape in the resin block according to the third
embodiment, and thus a step can be formed in each boundary of the
depressions 81 and 82.

[0103]As shown in FIG. 10(a), the longitudinal width of the resin block
56c is step-like decreased from both laterals to the center and is
step-like increased at the center. The longitudinal width in the
depression 81 is constant. As shown in FIG. 10(b), the upper depressions
81 are recessed downwardly. In one aspect, the vertical length of the
depressions 81 is constant almost all over the lateral direction, and the
bottom side of the depressions 81 is parallel to the top surface 71 of
the resin block 56c. As shown in FIG. 10(c), the upper end and the lower
end of the resin block 56c have a width smaller than the vertical center.

[0104]Therefore, in the V-shaped belt 31 according to the third
embodiment, the heat-radiating area of the resin blocks 56c can be
enlarged and clearances can be formed between the neighboring resin
blocks 56c. As a result, the heat-radiating property of the resin blocks
56c is improved, and thus the deterioration of the V-shaped belt 31 due
to the generation of heat can be suppressed.

[0105]FIGS. 11(a) to 11(c) show a resin block 56d of the V-shaped belt 31
according to a fourth embodiment. In the resin block 56d according to the
fourth embodiment, a depression 81 is formed in the upper front and rear
surfaces and a depression 82 is formed in the lower front and rear
surfaces. A depression 84 connecting the upper depression 81 to the lower
depression 82 is formed at the center of the resin block 56d. A
circumferential portion 85 extending approximately vertically is formed
at both sides of the depression 84. In the resin block 56d according to
the fourth embodiment 4, since the depressions 81, 82, and 84 are
vertically connected to each other, an approximately I-shaped depression
vertically extending in the resin block 56d as a whole is formed. Other
construction is similar to the resin block 56d according to the second
embodiment.

[0106]Therefore, in the V-shaped belt 31 according to the fourth
embodiment, the heat-radiating property of the resin blocks 56d can be
improved to thereby suppress the deterioration due to the generation of
heat. In addition, in the fourth embodiment, since the depression 84 is
formed at the vertical center of each resin block 56d, it is possible to
efficiently cool the center of the resin blocks 56d. Heat can most easily
stay at the center of the resin blocks 56d. Therefore, according to the
fourth embodiment, since the portion in which the heat easily stays can
be directly cooled, it is possible to further improve the heat-radiating
property of the resin blocks 56d. Therefore, it is possible to further
suppress the deterioration of the V-shaped belt 31 due to the generation
of heat.

[0107]FIGS. 12(a) to 12(c) show a resin block 56e of the V-shaped belt 31
according to a fifth embodiment. The resin block 56e is obtained by
removing the circumferential portion 85 of the center depression 84 from
the resin block 56d according to the fourth embodiment. Therefore, in the
fifth embodiment, since the center portion in which the heat can easily
stay can be directly cooled, thereby improving the heat-radiating
property of the resin block 56d.

[0108]In the second to fifth embodiments described hitherto, the
longitudinal widths in the upper end and the lower end of the resin
blocks 56b to 56d are constant. However, the shapes of the ends of the
resin blocks 56b to 56d are not limited. For example, the ends of the
resin blocks 56b to 56d may be formed tapered. Next, embodiments in which
the end shapes of the resin blocks 56b to 56d are modified will be
described.

[0109]FIG. 13 shows a V-shaped belt 31 according to a sixth embodiment. In
the sixth embodiment, the upper and lower ends of the resin blocks 56e
have the front and rear edges obliquely cut out. That is, the ends are in
a chamfered shape. As a result, in the sixth embodiment, the clearances
83 formed between the neighboring resin blocks 56e is widened toward the
opening end (in other words, the exit and entrance side of the air).

[0110]In the V-shaped belt 31 according to the sixth embodiment, since the
opening end of the clearances 83 is widened, the air can easily enter the
clearances 83. As a result, it is possible to further improve the
heat-radiating property of the resin blocks 56e.

[0111]FIG. 14 shows a V-shaped belt 31 according to a seventh embodiment.
In the seventh embodiment, the upper and lower ends of the resin blocks
56f have the front and rear edges obliquely cut out. However, in the
seventh embodiment, the edges are in a shape longitudinally cut out from
the longitudinal center position thereof. Therefore, the ends of the
resin blocks 56f have a pointed shape with an acute angle.

[0112]According to the seventh embodiment, since the opening end of the
clearances 83 is widened, the air can easily enter the clearances 83. As
a result, it is possible to improve the heat-radiating property of the
resin blocks 56f.

[0113]FIG. 15 shows a V-shaped belt 31 according to an eighth embodiment.
In the eighth embodiment, the upper and lower ends of the resin blocks
56g have a sectional shape of a circular arc. As a result, the width of
the clearances 83 varies continuously and slowly. Accordingly, since the
area of a flow path in the clearances 83 is not rapidly changed, the air
can be smoothly introduced into the clearances 83. Therefore, it is
possible to improve the heat-radiating property of the resin blocks 56g.

[0114]In the sixth to eighth embodiments, only the ends of the resin
blocks 56e to 56f have a partially narrowed tip. However, the entire
portions of the resin blocks from the vertical center to the ends may be
formed to have a narrowed tip. Next, embodiments in which the entire
portion from the center to the ends of the resin block is formed to have
a slowly narrowed tip will be described.

[0115]FIG. 16 shows a V-shaped belt 31 according to a ninth embodiment. In
the ninth embodiment, the upper and lower ends of a resin block 56h are
formed in a shape that the entire portions from the center to the ends
are obliquely cut out. As a result, the width of the clearances 83 is
slowly widened from the center to the ends. Therefore, since the air can
easily flow in the clearances 83, it is possible to improve the
heat-radiating property of the resin blocks 56h.

[0116]FIG. 17 shows a V-shaped belt 31 according to a tenth embodiment. A
resin block 56i according to the tenth embodiment has a shape that the
ends of the resin block 56h according to the ninth embodiment are further
chamfered. In other words, the resin block 56i has a shape that the ends
are narrowed in two steps from the center to the ends. According to the
tenth embodiment, since the entrance of the clearances 83 is further
widened, the air can more easily flow in the clearances 83. Therefore, it
is possible to improve the heat-radiating property of the resin blocks
56i.

[0117]FIG. 18 shows a V-shaped belt 31 according to an eleventh
embodiment. A resin block 56j according to the eleventh embodiment has a
shape that the ends are narrowed in two steps from the center to the
ends. However, in the eleventh embodiment, the ends are formed in a
pointed shape with an acute angle. According to the eleventh embodiment,
since the entrance of the clearances 83 is widened, the air can more
easily flow in the clearances 83. Therefore, it is possible to improve
the heat-radiating property of the resin blocks 56j.

[0118]FIG. 19 shows a V-shaped belt 31 according to a twelfth embodiment.
A resin block 56k according to the twelfth embodiment has a shape that
the edges are cut out from the center to the ends into a tapered shape
with an acute angle. According to the twelfth embodiment, since the
entrance of the clearances 83 is further widened, the air can more easily
flow in the clearances 83. Therefore, it is possible to improve the
heat-radiating property of the resin blocks 56k.

[0119]FIG. 20 shows a V-shaped belt 31 according to a thirteenth
embodiment. In the thirteenth embodiment, the sectional shape of the
resin blocks according to the second to fifth embodiments is changed to
the same shape as the first embodiment. That is, in the thirteenth
embodiment, the longitudinal width of a resin block 56l is smoothly
decreased from the center to the ends. The outline of the ends of the
resin block 56l forms a convex curve toward the tip. According to the
thirteenth embodiment, as described in the first embodiment, the air can
smoothly flow in the clearances 83 along the curved shape of the resin
block 56l. As a result, since the air can easily flow in the clearances
83, it is possible to improve the heat-radiating property of the resin
blocks 56l.

[0120]As described above, by continuously or step-like reducing the width
of the resin block from the center to the ends in the longitudinal
section of the resin block, the clearances can be formed between the
neighboring resin blocks so as to be widened from the center to the ends
of the resin blocks. As a result, since the air can easily flow in the
clearances, it is possible to effectively improve the heat-radiating
property of the resin blocks.

[0121]The V-shaped belt according to the present invention is not limited
to the above-mentioned embodiments but may be embodied in various forms.
In the embodiments, the depressions 81 and 82 are formed in all the resin
blocks. However, the depressions 81 and 82 may be formed in only a part
of the resin blocks. That is, in a part of the V-shaped belt, a plurality
of resin blocks in which the depressions 81 and 82 are formed may be
connected through the connecting member. Therefore, the V-shaped belts
obtained by combining the resin blocks having the depressions 81 and 82
and the resin blocks having no depression belong to the scope of the
present invention. By preparing plural kinds of resin blocks in which
depressions having different shapes and sizes are formed and combining
these resin blocks of different kinds, it is also possible to constitute
a V-shaped belt 31.

[0122]For example, as shown in FIG. 21, first resin blocks 56m having the
depressions and resin blocks 56n having no depression may be alternately
arranged in the length direction of the connecting member 57. Such a
V-shaped belt 31 can improve the heat-radiating property. In a V-shaped
belt in which a plurality of resin blocks are generally connected to each
other, when the connecting member is loosened, high-frequency vibration
may occur in the V-shaped belt. However, in the V-shaped belt described
above, since the resin blocks 56m having the depressions and the resin
blocks 56n having no depression are mixed, the resonant frequency can be
dispersed. Therefore, it is possible to suppress the vibration and noises
of the V-shaped belt 31. In addition, even when plural kinds of resin
blocks having the depressions are formed at different positions or plural
kinds of resin blocks having the depressions formed in different shapes
or sizes are combined, it is possible to reduce the vibration and noises,
similarly to the V-shaped belt 31 shown in FIG. 21.

[0123]As described above, various embodiments of the present invention are
applicable to a V-shaped belt, a belt-type transmission having the
V-shaped belt, and a saddle-type vehicle.

[0124]While the description above refers to particular embodiments of the
present invention, it will be understood that many modifications may be
made without departing from the spirit thereof. The accompanying claims
are intended to cover such modifications as would fall within the true
scope and spirit of the present invention.

[0125]The presently disclosed embodiments are therefore to be considered
in all respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims, rather than the
foregoing description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be embraced
therein.